(1) Field of the Invention
This invention relates to a flexible magnetic recording disk with excellent dimensional stability, isotropy of dimensional changes in the disk plane, and improved electromagnetic conversion properties.
(2) Description of the Prior Art
Flexible magnetic recording disks have already been known and come into use. (Refer, for example, to U.S. Pat. No. 4,223,361.) They comprise a biaxially oriented base of polyester film and a magnetic layer formed thereon by either applying magnetic particles together with a binder or by depositing a magnetic metal material on the base surface by vacuum metallizing, sputtering, ion plating, electro-deposition or other techniques.
The known magnetic recording disks, which undergo substantial dimensional changes with humidity variations, have disadvantages in that they tend to develop off-line of the track, or track shift, and lowering or fluctuation of the output upon changes in the ambient humidity.
Magnetic recording disks based on a biaxially oriented polyolefin film have also been known in the art. Their dimensional changes with humidity are negligible but those with temperature are serious and anisotropic in the disk plane. These drawbacks, sometimes combined with unsatisfactory electromagnetic conversion properties, have held back the commercial acceptance of the polyolefin film-based disks.